Evaluation of oxidative stress and antioxidant status of pregnant women suffering from malaria in Cameroon.

Oxidative stress is thought to be involved in the pathophysiology of malaria, especially in pregnancy where natural resistance is markedly reduced. In the present study we investigated oxidative stress in 315 pregnant women out of which 159 had Plasmodium falciparum malaria and 154 controls. We evaluated the level of lipid peroxidation products (MDA level) in the plasma, the activity of erythrocyte antioxidant defense enzymes, superoxide dismutase (SOD, EC: 1.15.1.1) and catalase (Cat, EC: 1.11.1.6) as well as the ability to resist oxidative stress by the FRAP (Ferric Reducing Ability of Plasma) assay. Total erythrocyte protein levels were also examined. For the two groups of patients, several differences between the biochemical parameters tested were found. Median parasitaemia in women with malaria was 25,392 parasites/µl of blood (Range1200-82000), while in controls we had no parasites found in thin and thick smears. Levels of lipid peroxidation products (MDA) were significantly higher in patients with parasitemia than in healthy asymptomatic volunteers (mean: 0.844 ± 0.290 and 0.384 ± 0.129 respectively, p<0.001). This MDA level was higher in primigravidea and also correlates well with parasite density (p<0.001). Catalase activity in erythrocytes of women with malaria did not differ statistically from that of controls. In contrast, SOD activity of patients with malaria was found to be significantly higher than that of controls (mean: 0.7899 ± 0.2777 and 0.4263 ± 0.2629 respectively, p<0.05). FRAP values declined, from parasitemic patients (1.4619 ± 0.6565) compare to controls (2.4396 ± 0.8883, p<0.05), particularly in the first and third trimester of gestation (p<0.05 and p<0.01 respectively). Finally, total erythrocyte protein concentrations of women with malaria did not differ from that of the controls. Our results suggest an imbalance between oxidants and antioxidants in pregnant women suffering from malaria, a situation which could lead to severe damage for either the mother or the fetus. Therefore, further research should be done to assess the potential benefits of antioxidant supplementation for the pregnant women suffering from malaria.

Assaying lipase activity from oil palm fruit (Elaeis guineensis Jacq.) mesocarp.

The mesocarp of mature oil palm fruit undergoes intensive triglycerides hydrolysis upon abscission and bruising. This generates such a high amount of free fatty acids that the oil might become unfit for human consumption without appropriate refining. The lipase (EC 3.1.1.3) involved in the breakdown of the oil is not stable after homogenization of the tissue in aqueous buffers. In this study, we have devised a solvent-based procedure that allowed us to obtain fractions with stable lipase activity. Using these fractions, we have determined the optimal conditions for assaying mesocarp lipase activity. The activity was highest at a temperature of 35 degrees C and a pH of 9. The lipase was found to be strictly calcium dependent. The specific activity of the lipase measured in optimal conditions was found to be 33 mumol fatty acids released min(-1) mg(-1) protein using olive oil as substrate. The mesocarp contains about 190 U of lipase g(-1) fresh weight. This activity was found to be inhibited by the lipase inhibitor tetrahydrolipstatin (THL), suggesting that the lipase is a serine hydrolase.

Antifungal Activity of Chromolaena odorata (L.) King & Robinson(Asteraceae) of Cameroon.

An aqueous ethanol extract of leaves of Chromolaena odorata and some of its fractions were examined for their antifungal properties by dilution methods on solid and liquid media, using yeasts and filamentous fungi. Extract and fractions inhibit the in vitro growth of Cryptococcus neoformans, Microsporum gypseum, Trichophyton mentagrophytes and Trichophyton rubrum with a minimal inhibitory concentration range from 62.5 to 500 microg/ml for the extract and from 25 to 100 microg/ml for fractions. A qualitative chemical analysis of the extract and fractions showed the presence of biologically active constituents such as some coumarins, flavonoids, phenols, tannins and sterols. No toxic effect was observed in mice treated per os with the extract. This study provides a scientific confirmation of the use of Chromolaena odorata in traditional medicine.

Evaluation of five essential oils from aromatic plants of Cameroon for controlling food spoilage and mycotoxin producing fungi.

Five essential oils (EO) extracted from Cymbopogon citratus, Monodora myristica, Ocimum gratissimum, Thymus vulgaris and Zingiber officinale were investigated for their inhibitory effect against three food spoilage and mycotoxin producing fungi, Fusarium moniliforme, Aspergillus flavus and Aspergillus fumigatus. Five strains of each fungus were tested. The agar dilution technique was used to determine the inhibitory effect of each EO on the radial growth of the fungus, and a dose response was recorded. The EO from O. gratissimum, T. vulgaris and C. citratus were the most effective and prevented conidial germination and the growth of all three fungi on corn meal agar at 800, 1000 and 1200 ppm, respectively. Moderate activity was observed for the EO from Z. officinale between 800 and 2500 ppm, while the EO from M. myristica was less inhibitory. These effects against food spoilage and mycotoxin producing fungi indicated the possible ability of each essential oil as a food preservative. A comparative test on the preservative ability of the EO from O. gratissimum and potassium sorbate against A. flavus at pH 3.0 and 4.5 showed that the EO remained stable at both pH, whereas the efficacy of potassium sorbate was reduced at higher pH. We concluded that the EO from O. gratissimum is a potential food preservative with a pH dependent superiority against potassium sorbate, and these are novel scientific information.

Antifungal activity of Piper guineense of Cameroon.

The antifungal activity of the ethanol extract of the seeds of Piper guineense and some of its fractions obtained by column chromatography was investigated using filamentous fungi and yeasts. The results indicated a significant antifungal effect. No toxic effect was observed in mice treated per os with the extract.

Streptococcus pneumoniae type XIV polysaccharide: synthesis of a repeating branched tetrasaccharide with dioxa-type spacer-arms.

beta-Glycosides of 2-acetamido-2-deoxy-D-glucopyranose were synthesised, using either 7-methoxycarbonyl-3,6-dioxa-1-heptanol or 8-azido-3,6-dioxa-1-octanol. Selective beta-lactosylation of 7-methoxycarbonyl-3,6-dioxaheptyl 2-acetamido-3-O-benzyl-2-deoxy-beta-D-glucopyranoside with hepta-O-acetyl-lactosyl-trichloroacetimidate, followed by beta-galactosylation of the secondary hydroxyl group with O-(2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl)trichloroacetimida te, catalytic hydrogenolysis, and O-deacetylation, gave 7-methoxycarbonyl-3,6-dioxaheptyl 2-acetamido-2-deoxy-4-O-beta-D-galactopyranosyl-6-O-(4-O-beta-D- galactopyranosyl-beta-D-glucopyranosyl)-beta-D-glucopyranoside. Selective beta-lactosylation of 8-azido-3,6-dioxaoctyl 2-acetamido-3-O-benzyl-2-deoxy-beta-D-glucopyranoside with hepta-O-acetyl-lactosyl bromide in the presence of silver triflate, followed by condensation with 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide in the presence of silver triflate, catalytic hydrogenolysis, and O-deacetylation, gave 8-azido-3,6-dioxaoctyl 2-acetamido-2-deoxy-4-O-beta-D-galactopyranosyl-6-O-(4-O-beta-D- galactopyranosyl-beta-D-glucopyranosyl)-beta-D-glucopyranoside.

Chemical synthesis of the human blood-group P1-antigenic determinant.

Condensation of known benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-4-O-(2,3,6-tri-O-benzyl-beta-D- galactopyranosyl)-alpha-D-glucopyranoside with 2,3,4,6-tetra-O-benzyl-alpha-D-galactopyranosyl chloride in dichloromethane in the presence of 2,4,6-trimethylpyridine, silver triflate, and molecular sieve 4A gave benzyl O-(2,3,4,6-tetra-O-benzyl-alpha-D-galactopyranosyl)-(1 leads to 4)-O-(2,3,6-tri-O-benzyl-beta-D-galactopyranosyl)-(1 leads to 4)-2-acetamido-3,6-di-O-benzyl-2-deoxy-alpha-D-glucopyranoside. Catalytic hydrogenolysis gave crystalline O-alpha-D-galactopyranosyl-(1 leads to 4)-O-beta-D-galactopyranosyl-(1 leads to 4)-2-acetamido-2-deoxy-alpha -D-glucopyranose, the human blood-group P1-antigenic determinant. A similar sequence of reactions was performed starting from allyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-beta-D-glucopyranoside, in order to prepare a derivative of this determinant suitable for linkage to carrier molecules.